[FFmpeg-cvslog] avcodec/alacdsp: Fix invalid shift in append_extra_bits()

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Sun Apr 26 19:29:39 2020 +0200| [49ae034b42234486712a02f9b00253a0975cea02] | committer: Michael Niedermayer

avcodec/alacdsp: Fix invalid shift in append_extra_bits()

Fixes: left shift of negative value -1
Fixes: 21390/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALAC_fuzzer-6242539519868928

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=49ae034b42234486712a02f9b00253a0975cea02
---

 libavcodec/alacdsp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/alacdsp.c b/libavcodec/alacdsp.c
index ecbaedb067..9996eb4319 100644
--- a/libavcodec/alacdsp.c
+++ b/libavcodec/alacdsp.c
@@ -49,7 +49,7 @@ static void append_extra_bits(int32_t *buffer[2], int32_t *extra_bits_buffer[2],
 
     for (ch = 0; ch < channels; ch++)
         for (i = 0; i < nb_samples; i++)
-            buffer[ch][i] = (buffer[ch][i] << extra_bits) | extra_bits_buffer[ch][i];
+            buffer[ch][i] = ((unsigned)buffer[ch][i] << extra_bits) | extra_bits_buffer[ch][i];
 }
 
 av_cold void ff_alacdsp_init(ALACDSPContext *c)